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c6 cell organism test Flashcards

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1
Q

Define species.

A

The smallest group of similar organisms that can interbreed with each other to produce fertile offspring.

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2
Q

Describe the system of scientific names.

A
  • The scientific name itself is unique to all the people (there are no 2 organisms that have an identical scientific name)
  • The first term is the genus, 2nd term is the species.
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3
Q

Define genus.

A

A classification below family and above species. E.g. rose is a genus and hybrid is a species.

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4
Q

List the 5 kingdoms.

A
  • Bacteria/ Monera
  • Protists
  • Animals
  • Plants
  • Fungi
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5
Q

Describe the difference between prokaryotic and eukaryotic. (further explanation of prokaryotes)

A

Prokaryotic= no nucleus
eukaryotic= has a nucleus
Prokaryotes lack internal membrane-bound organelles, do not have a nucleus, are significantly smaller than eukaryotes, usually existing as single cells.

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6
Q

Define saprophytic.

A

Feed on dead substances.

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7
Q

Define parasitic.

A

Obtain nutrients from living organisms.

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8
Q

Autotrophic

A

Produces its own food.

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9
Q

heterotrophic

A

Eats other animals or organisms.

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10
Q

Describe the characteristics of Prokaryotes.

A
  • surrounded by a cell wall
  • DNA moving freely within the cytoplasm
  • lack some other internal compartments (not only nucleus)
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11
Q

What are the only 2 prokaryotic cells left on the planet?

A

Bacteria an archaea

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12
Q

What are some key differences between prokaryote and eukaryote cells?

A
  • cell wall
  • no membrane-bound nucleus
  • no membrane-bound organelles (EXCEPT RIBOSOMES)
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13
Q

What are some major organelles inside a prokaryotic cell?

A

Plasma membrane, cell wall, genetic material, ribosome, cytoplasm

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14
Q

What are the 3 different kinds of cytoskeleton fibres?

A

Actin fibres, microtubules, and intermediate fibres.

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15
Q

Describe the function and type of cytoskeleton in eukaryote cells.

A
  • microscopic protein fibre
  • provides structural framework for the cell and its organelles
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16
Q

Can cell organelles be found in prokaryotic cells?

A

Only ribosomes can be found in prokaryotic cells. (none of the others)

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17
Q

What is the substance found in between organelles inside a cell?

A

cytosol

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18
Q

Everything in a cell except the nucleus is __________.

A

Cytoplasm, including organelles and cytosol.

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19
Q

What is the cell membrane made of?

A

Phospholipid bilayer with embedded proteins.

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20
Q

Define hydrophobic.

A

Naturally repels water (FEAR

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21
Q

Define hydrophilic.

A

Have a tendency to mix with, dissolve in, or to be wetted by water. (LIKES

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22
Q

Define selectively permeable/ semi-permeable.

A

Some particles are able to travel through, while some cannot.

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23
Q

Describe the function of cholesterol in the phospholipid bilayer.

A

it regulates its fluidity b keeping the phospholipids close together.

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24
Q

Cell membrane structure (fluid mosaic) fill in the blanks

A

View powerpoint.

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25
Q

What is the name of the model of cell membrane?

A

fluid mosaic model.

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26
Q

List the key organelles within an animal cell and their function/structure/ who do they work with, where are they found. (NCERGLMCCNV)

A
  1. Nucleus: contains DNA, double membrane
  2. Cytoskeleton: acts as skeleton and muscle (provides shape and structure), helps move organelles around the cells made of 3 types of filaments: microtubules, actin filaments, intermediate filaments)
  3. Endoplasmic reticulum (rough and smooth)
    - highway of the cell, connected to nuclear membrane
    Rough: studded with ribosomes- makes proteins
    Smooth: no ribosomes- makes lipids
  4. Ribosome: site of protein synthesis, found attached to rough ER or floating free in cytosol, produced in nucleolus
  5. Glogi apparatus: looks like a stack of plates, stores/modifies/packages proteins (post office), transports molecules through vesicles (lil balls)
  6. Lysosome: garbage disposal of the cell- breaks down wastes with digestive enzymes
  7. Mitochondria: performs cellular respiration to release energy for the cell to use, double membrane, has its own strain of DNA
  8. Centrioles: aid in cell division, made of microtubules
  9. Cytoplasm: holds components of the cell at their places and protects them from damage, provides structure for the cell
  10. Nucleolus: sphere, produces and assembles the cell’s ribosomes
  11. Vesicles: A small sac formed by a membrane and filled with liquid. Vesicles inside cells move substances into or out of the cell.
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27
Q

Which organelles do lysosomes work with?

A

Rough ER -> Golgi apparatus -> Lysosome

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28
Q

List the key organelles within a plant cell. (in what cells are they found, structural features, what’s inside them)

A
  1. Chloroplasts: found only in plant cells, protists and monera; contains chlorophyll; site of food production (glucose); double membrane
  2. Cell wall: found in plant and bacterial cells, rigid protective barrier, located outside of cell membrane, made of cellulose (indigestible) fibre
  3. Large central vacuole: storage compartment for food, water, waste, enzymes (e.g. lysosome), pigments, etc.
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29
Q

What does having numerous mitochondria suggest in a cell?

A

Active transfer.

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30
Q

Humans aren’t able to break down cell wall on plants, but how do herbivores do it?

A

Microbes in their stomach are able to break down cell wall.

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31
Q

do fill in the blank of animal cell diagram

A

(google for ans)

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32
Q

Do fill in the blank of plant cell.

A

ans on google

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33
Q

Describe the functions of membranes.

A
  1. Protect cell
  2. Control incoming and outgoing substances
  3. Maintain ion concentrations of various substances
  4. Selectively permeable- allows some molecules in, some kept out.
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34
Q

what are the 2 things solutions are made of and laborite what they are.

A

Solvent- the liquid in which the solute is poured and dissolved. (e.g. water, alcohol, petrol)
Solute- substance that is dissolved or put into the solvent. (e.g. salts, sugars)

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35
Q

What are the 4 methods of transport across membranes?

A
  1. diffusion: movement of molecules from an area of high concentration to an area of low concentration
  2. osmosis
  3. facilitated diffusion
  4. active transport
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36
Q

What organelles can be seen with a light microscope?

A

Nucleus, nucleolus, large central vacuole, cell membrane, chloroplast, cytoplasm, cell wal

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37
Q

What organelles can be seen with an electron microscope?

A

Any organelles.

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38
Q

Define un-facilitated

A

Passive

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39
Q

Describe diffusion.

A

movement from one side of a membrane to another, un-facilitated.

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40
Q

Define osmosis.

A

Water moving from a high concentration of water (less solute) to a low concentration of water (more solute).
-> water would cross a selectively permeable membrane from a dilute solution to a concentrated solution (more dissolved in it).

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41
Q

Define: dilute solution.

A

Lots of water, less solute.

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42
Q

Define: concentrated solution

A

Less water, more solute.

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43
Q

Define: net movement of water

A

The direction most of the water is travelling in.

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44
Q

What direction is water moving towards around a membrane?

A

Water is always moving both ways across a membrane.

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45
Q

What is another name for cell membrane?

A

Plasma membrane.

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46
Q

Define concentration gradient.

A

The measurement of concentration change as particles travel across one membrane to another.

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47
Q

Define isotonic.

A

When the concentration gradient is 0, where the 2 sides have exactly the same amount of the same particle.

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48
Q

Define facilitated diffusion.

A

The passive movement of molecules across the cell membrane via the aid of a membrane protein.
- Utilised by molecules that are unable to freely cross the phospholipid bilayer (e.g. large, polar molecules and ions)

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49
Q

Define active transport.

A

When enzymes use energy in the form of ATP to transport molecules against a concentration gradient
-> moving water towards a diffused solution.

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50
Q

How are molecules travelling through a membrane?

A

Through microscopic pores in the membrane.

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51
Q

Define: hypertonic solution

A

Low amount of solute, less salts than cytosol (water)>

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52
Q

Define: hypertonic solution with an example

A

High amount of solute, more salts than the cytosol. (e.g. dead sea)

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53
Q

When the membrane allows only allows molecules of a certain size to diffuse thru it, it is _______

A

Selectively permeable.

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54
Q

Define: cytolysis

A

dissolution or disruption of cells.

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55
Q

What is another word for swell?

A

Turgid.

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56
Q

Cytolysis

A

Cytolysis is a cell death which occurs as the result of a rupture in the cell’s membrane. When a cell experiences cytolysis, it bursts, scattering its contents in the process.

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57
Q

Plasmolysis (definition and process)

A

Plasmolysis is the process of shrinking of plasma membrane from the cell wall when the cell is placed in a hypertonic solution. This happens due to exosmosis as water moves out of cell into the solution.
water leaves cell -> shrink -> membrane pulls away from cell wall -> no structure -> wilts

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58
Q

Describe and explain the relationship between surface area to volume ratio and diffusion rate.

A

The larger the surface area:volume ratio is, the higher the diffusion rat. As that means the substance has more surface area to diffuse across, despite having a smaller volume.

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59
Q

Define osmoregulation (and what is it a form of?)

A

the process of maintaining salt and water balance (osmotic balance) across membranes within the body- form of homeostasis.
Done by keeping the concentration of body fluids outside the cell the same as it is inside.

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60
Q

What is an example of osmoregulation in the body?

A

Excess water in the body that is not used goes to the bladder and gets excreted. (contains harmful urea)

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61
Q

Describe the process of osmosis between cells.

A

If the concentration of the cell sap (liquid inside large central vacuole of cell) is greater in one cell than in its neighbour, water will pass by osmosis from the less concentrated to the more concentrated.

62
Q

cell division followed by cell expansion causes ______

A

growth

63
Q

Active transport requires energy, so what is the outcome of that?

A
  • heat is given off
  • oxygen is used up
  • co2 produced
  • glucose used up
64
Q

What are the 2 main types of active transport? Explain what they do.

A
  • Endocytosis: taking particles into a cell
  • Exocytosis : when vacuoles expel their contents to the outside (e.g. osmosis)
65
Q

What are the two types of endocytosis?

A

Engulfing a liquid= pinocytosis
Engulfing a solid= phagocytosis

66
Q

Describe the process of osmosis within a plant. (non-growing regions)

A
  • The cell membrane acts as a selectively permeable membrane
  • the cell wall is freely permeable to water
  • The vacuole contains a solution of salts and sugars (*concentrated solution)
  • water diffuses into the vacuole if there is water outside the cell
  • vacuole expands, pushing cytoplasm outwards against the cell wall and makes the plant turgid.
  • the pressure of the vacuole against the cell wall makes the cell very firm because the cellulose cell wall cannot stretch
67
Q

Describe osmosis in a plant (growing region)

A
  • CELL WALLS ARE EXPANDABLE AND SAID TO BE STILL PLASTIC
  • when the vacuole takes in water, it expands, pushing out on the cell wall, and increasing the size of the cell
68
Q

cell division at a growing point increases ________ but cell expansion causes the increase in _________.

A
  1. number of cells
  2. size
69
Q

Describe the function of a contractile vacuole in a cell.

A

It expands to push the excess water out of a cell to prevent it from bursting.

70
Q

red blood cell (location and SA(structure):function)

A
  • Blood (animal)
    Biconcave - Large surface area for absorbing oxygen
  • no nucleus so they won’t carry it mitosis/meiosis
71
Q

Muscle cell (location and SA:function)

A
  • found in the muscles (animal
  • can stretch to allow lengthening of muscles
72
Q

Egg cell (location and SA:function)

A
  • found in the ovary (animals and plants)
  • contains large food storage and genetic material to grow and develop
  • Lots of energy for growth
  • 1/2 DNA
73
Q

Sperm cell (location and SA:function)

A
  • Testes (animal)
  • Long flagellum which allows cell to swim
  • Lots of mitochondria to power movement
  • Enzymes in the head to break into egg cell
  • carries DNA
74
Q

Xylem cell (location and SA:function)

A
  • found in the plant stem (plant)
  • acts like a straw and draws water up the plant, function is transpiration
  • hollow to carry water
    DEAD
75
Q

Pollen cell (location and SA:function)

A
  • anther (plant) (the juicy bit that contains pollen)
  • small and light to be easily transferred to the egg cell in the plant
  • lots of energy
  • 1/2 DNA
76
Q

Root hair cell (location and SA:function)

A
  • found in the plant root (plant)
  • large perturbation maximises SA:V, therefore maximises water absorbed into plant cells
  • no chloroplast
  • has lots of mitochondria
77
Q

Palisade cell (location and SA:function)

A
  • found in the leaf of plant
  • transparent, regular shaped cells with chloroplasts for photosynthesis
  • prevent water getting out and stopping unwanted substances/organisms getting in.
  • not many mitochondria because they don’t require a lot of energy
78
Q

ciliated epithelial cell (structure v.s. function)

A

Cilia, external
- lines cavities (e.g. airways) (animal)
- cilia all beat together to move mucous and trapped particles up&out of the trachea
- prevents aspiration (particles entering lungs and causing infection)

79
Q

Nerve cell (neurone) (structure v.s. function)

A
  • connect sensors to the brain (animal)
  • long length for transmitting signals over a long distance quickly
    (GO OVER STRUCTURE)
80
Q

Describe the difference between function of mitosis and meiosis.

A

Mitosis: growth, replace worn out cells, repair damaged tissue
Meiosis: sex cells

81
Q

what is differentiation of cells.

A

Differentiation is the ability of cells to become different shapes or sizes to carry out specialised jobs

82
Q

What are the difference between multicellular and unicellular organisms?

A

A unicellular organism depends upon just one cell for all of its functions while a multicellular organism has cells specialized to perform different functions that collectively support the organism.
therefore multicellular…
- can grow larger
- more complex

83
Q

What is the cell theory?

A
  1. All organisms are made of cells
  2. All existing cells are produced from a previous cell
  3. A cell is the most basic sub-unit of life.
84
Q

How many chromosomes do human cells contain?
These pairs are said to be _________.

A

23 pairs, 46 chromosomes in total.
Homologous.

85
Q

A cell that has pairs of chromosomes is said to be ______.

A

Diploid.

86
Q

All cells except for ________ are diploid. Why?

A

Sex cells.
Because they will be paired with egg cell/ sperm cell that gives them the other half.

87
Q

In mitosis, the new cells are __________ to the original cell.

A

Genetically identical.

88
Q

Cilium (function, structure)

A

A cilium, or cilia (plural), are small hair-like protuberances on the outside of eukaryotic cells. They are primarily responsible for the movement of the cell or fluids on the cell surface., either of the cell itself or of fluids on the cell surface.

89
Q

Flagellum (function, structure)

A

A hairlike external body part that protrudes from certain plant and animal sperm cells, and from a wide range of microorganisms to provide motility.

90
Q

Define equilibrium in cells

A

When the concentration gradient is 0- isotopic solutions.

91
Q

Significance of mitosis and meiosis in asexual and sexual reproduction as a source of genetic variation

A

Mitosis and meiosis both involve cells dividing to make new cells. This makes them both vital processes for the existence of living things that reproduce sexually. Meiosis makes the cells needed for sexual reproduction to occur, and mitosis replicates non-sex cells needed for growth and development.

92
Q

Describe the 5 stages of mitosis.

A
  1. Each chromosome is copied (DNA replication)
  2. Cell resting
  3. Spindle forms. Chromosomes arranged along the equator.
  4. Chromosome single strands get dragged to the poles of the cell.
  5. Two genetically identical cells are produced
93
Q

what cell does not have mitochondria, chloroplasts, and nucleus, but has a cell wall? (STATE CELL TYPE AND TYPE OF ORGANISM

A

Cell type: N/A
Organism type: bacteria

94
Q

what cells have few mitochondria, nucleus and cell wall but no chloroplasts?

A

Epidermal cell

95
Q

what is the formula for photosynthesis?

A

6CO2+6H2O→C6H12O6+6O2

96
Q

Guard cell: function, location
Stomata: function

A
  • Control gas diffusion by regulating opening and closure of stomatal pores
  • Found in the epidermis layer of plant
    STOMATA function: controls the rate of gas exchange, amount of water loss and gas loss is controlled by pore size and pressure
97
Q

Describe the process of water going up plant (xylem, guard cell)

A

Lots of water -> root hair cell -> stem -> xylem -> fills large central vacuole of stomata and pushes it open -> water loss by vapour

98
Q

Xylem cell: function, location, fun fact, what plant can they be found in

A
  • dead tissue
  • function: transports minerals and water from root to stem of the leaf
  • function: provides physical support for the plant
  • found in all vascular plants and all flowering plants
  • transpiration
99
Q

What is the word for molecules sticking together? Use it in the context of plants and water.

A

Cohesion
Cohesion draws up water to top for photosynthesis

100
Q

Transpiration

A

Water evaporating via passive movement

101
Q

Phloem (function and diffusion)

A
  • function: transport and distribution of sugars and organic nutrients produced by photosynthesis
  • translocation
  • A high concentration of organic substances, particularly sugar, inside cells of the phloem at a source, such as a leaf, creates a diffusion gradient (osmotic gradient) that draws water into the cells from the adjacent xylem. This creates turgor pressure, also known as hydrostatic pressure, in the phloem.
102
Q

what’s the word that describes motion of a human sperm cell?

A

Locomotion

103
Q

Describe the significance of a sunken stomata

A
  • stomata in a small pit
  • embedded into the leaf layers rather than on the surface of the leaves
  • protects against the escaping water vapor from air currents
  • decreasing water loss from the leaf
  • decreasing transpiration
104
Q

How can a unicellular, aquatic organism survive without complex structures like a multicellular organism?

A

Multicellular:
Lysosome for waste disposal
Smaller SA:V ratio (compared to unicellular organism
Slower diffusion rate
Complex structures to obtain substances like co2 for survival
Complex transport systems are necessary
Osmoregulation done by homeostatic processes
———————————————————
Unicellular:
Disposes of waste substances with diffusion
Very big SA:V ratio compared to multicellular organism
High diffusion rate
Relies on diffusion for survival
No need complex transport systems as diffusion rate is high
Osmoregulation with contractile vacuole

105
Q

What are some examples of a unicellular organism?

A

Amoeba, paramecium, euglena

106
Q

What is a stem cell?

A

A cell with the ability to differentiate into al the types of cells in the human body.

107
Q

How does a cell differentiate?

A
  • Switches off all the other genes except for the gene of the specialisation it wishes to have
108
Q

Name the process involved and give 2 reasons why substance Y had to be taken through structure B but not normally through the cell membrane.

A
  1. The substance is being transported against its concentration gradient (low concentration to high concentration.)
  2. a charged particle unable to be moved across the membrane
  3. substance y is too large to pass through the phospholipid bilayer.
109
Q

Is this a prokaryote or a eukaryote? Give TWO reasons for your answer.

A

have/ don’t: have membrane bound organelles
have/ don’t: have distinctive nucleus

110
Q

The cell illustrated (on the previous page) is adapted for the three functions listed below. Use the diagram to explain how this cell is adapted for each of these functions. Refer to a different structure(s) in the diagram for each of your answers.
(i) Rapid diffusion of substances from the lumen of the gut into the cytoplasm

A

Microvilli increased SA:V ratio of the cell which leads to an increased diffusion rate.

111
Q

Name two factors that could affect the rate of diffusion in cells, and explain the way in which they do this.

A
  • temperature
  • SA:V ratio
  • thin membrane
112
Q

Suggest a reason for the difference in the rate of beats per minute of the contractile vacuole, when the organism is moved from pond water to distilled water.

A
  • hypotonic/ hypertonic
  • type of diffusion, what happens with substance movement
  • direction of movement
  • reason for more/ less beating
  • refer to specific data

Distilled water is more hypotonic compared to pond water. Therefore, more water enters the cell by osmosis,
from a low to high concentration (1). The contractile vacuole must beat faster to remove the excess water (1

113
Q

Explain why the rate of contractile vacuole beats changes between 0.10% to 0.20% sodium chloride solution.

A
  • hypotonic/ hypertonic/ isotonic
  • type of diffusion, what happens with substance movement
  • direction of movement
  • reason for less/more/no beating
  • refer to specific data

As the salt concentration of the solution increases, it becomes less hypotonic. Therefore, less water enters the cell by osmosis (1). Less water needs to be expelled out of the cell, so the contractile vacuole beats at a lower rate (from 3.3 to 1.5 bpm

114
Q

Explain why the contractile vacuole stopped beating in 0.25% sodium chloride solution.

A
  • hypotonic/ hypertonic/ isotonic
  • type of diffusion, what happens with substance movement
  • direction of movement
  • reason for less/more/no beating
  • refer to specific data

At 0.25% the solution becomes isotonic to the cell. There is no overall net movement of water (1) into or out of the cell. The volume of the cell remains constant and the contractile vacuole does not need to beat (1).

115
Q

q3: Which of these cells would have the greatest surface area to volume ratio? Explain your choice. (pic in gallery- c6 test 2)

A

Cell A would have the highest SA: V ratio due to its villi/ microvilli, which maximizes its absorption of food.

116
Q

q3: Cell B is specialized cells. Name it and describe how its structure helps it to function including specialized organelles. (pic in gallery- c6 test 2)

A

Palisade cells. Its square/ rectangle structure allows it to stack tightly against each other. It has chloroplasts that conduct photosynthesis, where its stacking structure allows the plant to grow taller in order to maximize exposure to light.

117
Q

The movement of potassium ions is an important factor in the opening and closing of the stomata by guard cells. Explain the significance of the fact that guard cells contain chloroplasts.

A

Chloroplast conducts photosynthesis and produces glucose as a product. Glucose contributes to the osmotic gradient, added turgor increases pressure on the guard cell and opens the stomata.

118
Q

The turgor pressure inside guard cells is also an important factor in the opening and closing of the stomata by guard cells through a change in their shape. Explain how the movement of potassium ions into a guard cell will affect its turgor pressure.

A

The movement of potassium ions increases the solute concentration of the guard cell, causing osmosis to occur in order to achieve isotonic equilibrium. This leads to the cell swelling up and increasing turgor pressure, opening up the stomata.

119
Q

Tasc 2021 14a
The diagram below shows four possible set ups for an investigation looking at the movement of molecules.
W: 10% glucose, 37 c
X: 6% salt, 37c
Y: 6% glucose, 60 c
Z: 14% salt, 60 c
In which of the above would the level of the solution in the tube rise the fastest when the tube is placed in a breaker of distilled water? Give the reasons for your answer.

A
  • increase occurs when…
  • concentration gradient and rate of diffusion (connection between them)
  • when temp is different…
  • more molecular activity= higher rate of diffusion
    Z (½). An increase in the rate of diffusion occurs when the concentration of solute is higher
    or when the solute is the most/very hypertonic to the beaker (½). The greater the
    concentration gradient/ difference in concentrations (½) the faster the diffusion/ osmosis.
    When the temperature/ temperature difference is highest (½), the more kinetic energy
    (½) and the rate of molecule activity would increase (½) the higher the rate of diffusion.
120
Q

Give an example of a situation when an organism with a smaller SA:V ratio would have an advantage over an organism with a larger SA:V ratio in terms of its physiological adaptation to the environment. Explain your answer.

A

Organism D has a much smaller SA:V ratio compared to C, therefore it also has a much smaller diffusion rate. This can be beneficial in a poisonous solution, where the slower absorption rate of poison delays its impact. Where it would also be beneficial in a cold situation, where heat would be lost at a slower rate. (organisms with larger SA:V ratio would have to use lots of energy to keep themselves warm as their heat loses faster.

121
Q

Calculate the size of organelle ___ in both millimetres and micrometers.

A

(DRAW Measured longest length/ DRAW length of scale)*scale FOV length

122
Q

[C and D are both spheres, C is a much smaller sphere compared to D)
Which of the organisms C or D would turn completely red more quickly when placed in a red dye solution? Explain your answer.

A

C and D have the same shape but largely different sizes. C is much smaller than D but has a much larger SA:V ratio due to its size. Therefore C would turn red much more quickly than D when placed in a red dye solution as it has a much higher diffusion rate.

123
Q

Explain how water gets to these cells(guard cells) in the plant.

A

Water reaches these cells by cohesion through the root hair cell where it is absorbed from the soil to the xylem, and finally to the guard cell.

124
Q

Why would these cells be located in this position in the leave and why do they need to be near part VI?

A
  • need to be near the stomata to collect Co2 and water for photosynthesis
  • as well as being at the surface (upper part) of plant to collect as much sunlight as possible.
125
Q

cells test 2 q6cii (photo
(ii) Explain the decrease in the amount of DNA present at time R. (1 mark)

A

at time R the one cell has completely split cytokinesis(1/2) and formed two new cells so the existing cell has now the same amount of DNA as it began with.

126
Q

cells test 2 q5a (photo
(a) Using your knowledge of cells and the movement of substances across a membrane, outline and explain what has occurred in diagrams B and C. (3 marks)

A

(a) In cell B and C osmosis has occurred (½) which is the movement of water from a dilute solution to a stronger solution through a semi permeable membrane (1). The plant cell B and C is evidently in a hypertonic solutions (½)) It has lost water due to osmosis shown by the shrinking of its large vacuole. (1) C had a stronger concentration gradient so lost more water compare with B in the same time frame (1 minute). (1)

127
Q

cells test 2 q5b (photo
b) The procedure was repeated using human red blood cells which normally exist in plasma which has the equivalent concentration to 0.9% saline. Explain what you would expect to occur in each treatment. (3 marks)

A

(b) In red blood cells the 1% solution (B) would have been close to isotonic for the red blood cell and as such little change in water across the membrane would have been evident. In (A) solution fresh water would be an example of a Hypotonic solution and water would move into the cell by osmosis. This would continue until the cell would burst. (1) In solution C at 5% saline it is a hypertonic solution with reference to the cell and as such water would move out of the cell and cause it to shrivel up. (1)

128
Q

cells test 2 q1a (photo
(a) Name structures 1 and 3 (they are different) and discuss the difference in their function. (2 marks)

A

(a) Structure 1: Cell membrane & Structure 3 is cell wall / capsule (1 mark).
Differences in function: Cell membrane controls exchange of substances between the cell and its external environment (1 mark), whereas cell wall provides structural support and protection (which is enhanced by capsule especially) (1 mark).

129
Q

cells test 2 q1b (photo
(b) Which one of these diagrams, A or B, shows a prokaryotic cell? Give evidence from the diagram of your choice to support your answer. (2 marks)

A

Cell B is prokaryotic ( mark), Evidence: lacks membrane bound organelles (although this is hard to tell due to nature of diagrams), nuclear material not in a membrane bound nucleus, presence of capsule surrounding the bacterium (1 mark for each), Up to 1 mark for mentioning that bacteria are prokaryotic organisms while humans are not.

130
Q

cells test 2 q1c (photo
(c) Explain two ways in which the structure of the cells in A are suited to their specialised function (2 marks)

A

Cell A is suited to its function – cilia projections (micro – hairs) (1/2) on the edges of the cell filter the air by trapping debris such as dust, bacteria and other foreign matter from going into the lungs. (1) Directs the flow of air down the passage and foreign matter the opposite direction. (1/2) and gives protection. (students may mention mucus secretions by goblet cells but they are not pictures and we have not taught this yet.)

131
Q

b) Unicellular (or single celled) organisms must survive and carry out all processes to do so with
one cell.
Multicellular organisms such as plants and animals have many specialised cells.
Evaluate why multicellular organisms have so many different cell types while
unicellular organisms can be alive with just one. (6 marks)
Your evaluation should consider anything of relevance including:
* The role or function of the cell/s
* The environment the cell/s exists in
* SA:V ratio of the cell/s.
(6 marks)

A
  • ‘Cells exchange materials and wastes in an aqueous/interstitial fluid environment across a
    plasma membrane (1).
  • Concentration gradients and dissolved substances help increase the
    rate of exchange (1)’.
  • The complexity of an organism is largely due to its SA: Vol ratio (½).
  • An effective exchange with the environment requires sufficient material (nutrients such as glucose, gases O2 & CO2) to cover the whole body (½) and removal of waste (½), at a certain rate. As the volume of a cell increases so does the surface area but at a much smaller rate (½), hence creating a smaller SA: Vol ratio(½).
  • As the SA: Vol ratio decreases the efficacy of diffusion also decreases (½)as it takes longer for important nutrients to
    diffuse to all parts of the cell to keep it alive (as well as removal of waste).
  • Therefore, size becomes a limiting factor. (½)
    UNICELLULAR organisms are small in size and have an effective exchange rate (high rate of diffusion) (½) across a plasma membrane due to a large SA: Vol ratio and short
    diffusion distance (1).
  • Living in an aqueous environment requires specialised process such as osmoregulation or osmo-conforming, cilia or flagellum for movement (½) and transport processes (endocytosis, exocytosis) to maintain a homeostatic balance. (½)
    Multicellular organisms are larger and have smaller SA:V ratio (½) therefore with groups of cells (skin, muscle, blood, nerve etc.) (½) differentiating to take on work together (specialised functions) they can carry out metabolic processes and increase SA: V. (½)
    The metabolic process requires specialised cells and in most cases a transportation/circulatory system (½) (for movement of nutrients, gases and waste) (½) to carry out their function efficiently. Cells that require a large amount of diffusion
    to occur such as intestinal epithelium cells contain microvilli to increase the surface
    area (½) or red blood cells (specialised shape) have a biconcave shape to increase
    SA:V ratio hereby increase functionality (½), they will have a much larger SA: Vol ratio
    then storage cells (fat cells) that do not wish to lose what they are storing(½). Muscle
    cells require more mitochondria to carry out cellular respiration (½)to provide ATP
    for movement (½), white blood cells to fight infections belonging to the lymphatic
    system (½).
132
Q

The antibiotic tetracycline binds to ribosomes in bacterial cells. Suggest a reason as to why this
causes the death of bacterial cells. (2 marks)

A

As ribosomes are the site of protein synthesis (1), binding of tetracycline must stop this
process. If the bacteria cannot make the proteins it needs (½) (such as enzymes needed
in cellular reactions (½)), this must lead to death of the bacterial cell.

132
Q

Provide 2 pieces of evidence to show the process is mitosis. (2 marks)

A

Diagram C shows 2 daughter cells forming (1) marks
* 2 daughter cells form, whereas in meiosis 4 haploid cells form (1) mark
* There is only 1 round of cell division, meiosis undergoes 2 cell divisions (1) mark
* Identical daughter cells (½) or genetically identical daughter cells (1)
* Splits into two (½) mark
* If correct comparison with meiosis (½) mark

133
Q

Cellular structures are suited to their functions.
a) Cells that secrete enzymes contain a lot of rough endoplasmic reticulum (RER) and a large
Golgi apparatus.
Explain the role of these organelles and how they work together in the production of enzymes. (3 marks)

A

Enzymes are proteins (½). RER is the site where mRNA is read by ribosomes (three
nucleotides at a time) as the code is translated into polypeptides or proteins (1). The
RER then acts as channel for the proteins to move along towards the Golgi (½). The
Golgi is where the polypeptides may be combined into proteins, (½) or the already
formed proteins are packaged into vesicles for transport in or out of the cell (½).

134
Q

Analyse what the diagram would need to show in order to distinguish the difference between the two (2)
processes- diffusion and osmosis. (2 marks)

A

To distinguish between diffusion and osmosis: the diagram
would need to show water molecules moving down their concentration gradient by
osmosis (½). There would have to be solute concentrations identified on each side of
the membrane to determine which direction the water molecules would move (1). For
diffusion: gas or solute molecules (½) would need be in different concentrations on
either side of the membrane and arrow showing movement down their concentration
gradient (1) Different proteins identified – aquaporin for water molecules to move
through by osmosis or channel protein for charged ions or larger nutrients/solutes to
diffuse through (1).

135
Q

Which of these are present in a bacterial cell?
DNA, nuclear membrane, lysosome, vacuole, plasmid, ribosomes

A

dna, nuclear membrane, plasmid, ribosomes

136
Q

Which of these are present in a plant cell?
DNA, nuclear membrane, lysosome, vacuole, plasmid, ribosomes

A

dna, nuclear membrane, vacuole, ribosomes

137
Q

Why are algae eukaryotic cells but not classified as plants or animals? (2 marks)

A

Any plausible reasoning such as: Algae are eukaryotic cells as they have a defined nucleus
and membrane bound organelles. (1) Algae are not animal cells as they have a cell wall
and chloroplasts (½), they are not plant cells as they have a contractile vacuole (½),
they are likely to be neither and be a different classification such as protists (½).

138
Q

The size and shape of a cell limit the rate at which material can be exchanged with the
surrounding environment. Briefly explain the scientific basis of this statement, drawing on
examples you have studied.
(5 marks)

A

Size:
As the size of a cell increases, its volume increases much faster (x3
) than its surface area (x2
).
The smaller the cell, the greater its SA:Vol ratio and the more efficient it is at exchanging
materials.
At some particular size, the surface area will not allow the exchange of sufficient materials to
supply the needs of all the organelles which make up the volume of the cell. This limits the size of the
cell and explains why cells are usually microscopic.

Shape:
A sphere is the shape with the lowest SA:Vol ratio and is the least efficient at exchanging
materials. Any change in this shape (elongating, flattening, the presence of microvilli etc.) will
increase both the SA:Vol ratio and the efficiency of the cell.
The function of a cell may also determine its shape. Specialized cells that function to absorb
material (e.g. the cells that line the small intestine) or excrete material (e.g. kidney cells) have a
larger SA:Vol generally due to modifications like microvilli. Photosynthetic cells tend to be long
and thin which enhances SA:Vol ratio.
Active animal cells are smaller than less active cells or plant cells. Examples can be given here.
Some cells are specialized to have limited exchange of materials such as adipose tissue which
stores fat, dormant eggs in the ground or even some seeds. These have a low SA:Vol ratio and
are often spherical.

139
Q

Red blood cells were placed in an unknown solution. Electron microgaphs were taken at the
start of the experiment and after two minutes.
start: normal
after 2 minutes: puffed up
Explain fully what process is taking place. (3 marks)

A

The process is osmosis (½) because the RBC is swelling/ increasing in volume/ the solution
is entering the cell (½). The solution is moving from the hypotonic/ low solute conc./ high
water conc. (½) to the hypertonic/ high solute conc. / low water conc. Inside the RBC (½)
until equilibrium/isotonic environment is reached (½) or the RBC burst (haemolyse) (½).

140
Q

Penicillin is a substance which kills bacterial cells by damaging their cell walls. As a result,
they burst when they take in water.
Suggest why penicillin has no effect on plant cells. (2 marks)

A

Plant cell walls are made of cellulose and bacterial cells are made of polysaccharides and
amino acids (peptoglycan = murein) or are made of different material to bacterial cells (1).
The plant cell wall limits the size that the cell can swell to and therefore the amount of water
it can absorb, preventing it from bursting (1).

141
Q

explain how crossing over affects the
inheritance of genes. (1.5 marks)

A

. B (½) Crossing over mixes (½) up chromosomal material. This increases genetic variability
(½) in the gametes and ultimately the offspring. This results in offspring that are different
to their parents and each other (½). [other variations were awarded marks providing the
idea being expressed was the same].

142
Q

In what part of a plant or animal would you expect to find the cell as depicted above? Justify
your answer. (3 marks)
(cell with large central vacuole, cell wall, and chloroplast)

A

In the green part of a plant, a leaf or stem. It is a plant cell because of the presence of the
thick rigid cell wall to provide support. A large vacuole as reservoir of water and metabolites/
or to provide turgor/ or any reasonable function. Chloroplasts needed for photosynthesis.
½ mark each.

143
Q

Indicate if capsid, cell wall, flagellum, and plasmid are always absent or may be present in a bacteria and in a virus.

A

Feature Bacteria Viruses
Capsid A P
Cell wall P A
Flagellum P A
Plasma P A

144
Q

In which, mitosis or meiosis, does independent assortment occur?

A

meiosis

145
Q

Discuss how the structures relate to function in bacteria and viruses. (4 marks)

A

Virus:
have a protein coat (capsid) surrounding it for protection (1
often have spikes that allows it to stick to host cells(1
covered in surface proteins that allows it to enter and exit a host cell (1
contain DNA or RNA that allows them to replicate on a host cell (1
extremely small allowing them to infiltrate host cells easily and replicate in large numbers (1
Bacteria:
contains ribosomes to make proteins (1
cell wall giving protection (1
capsule coated cell wall protecting against antibiotics (1
very small for high sa:v ratio for fast diffusion of materials (1
contains plasmids with genes that enhance survival of bacteria (1
shape of some allows stacking, to take up area efficiently when multiplying (1
extremely small, enabling easy entrance into body (1

146
Q

in which, or both, eukaryotic and prokaryotic cells, are ribosomes found?

A

both

147
Q

Explain how the relationship between surface area and volume affects the movement of substances into and out of a cell; and as a result, the rate of metabolic activity in the cell and the cell’s efficiency.

Use several examples in your answer and show how the SA:V ratio varies depending on the type and function of the cell. (5 marks)

A

Cells need to exchange materials such as nutrients and waste products with their environment
through their cell membrane (1). A cell with a larger volume must support this with more
metabolic activity. (1) A large SA:V means more capacity for material exchange as there is
more surface area supporting the volume (1), with smaller diffusion distances (1).
This is particularly important for cells that have a secretory role (such as those secreting
enzymes) or absorption role (intestinal epithelium) that have higher metabolic rates (1). A
small SA:V would be more beneficial to cells storing substances (such as fat/adipose cells), with
a lower metabolic rate, as they need to contain material and not exchange it (1).
At least two examples of cells needed to be included for full marks.

148
Q

Selectively permeable membranes are crucial to the viability of cells.
1) To what extent is the cell (plasma) membrane responsible for the cell’s homeostatic balance. Briefly discuss its role in the regulation of the cell’s internal environment. (3 marks)

A

The cell membrane is selectively permeable and regulates what enters and leaves the cell.

Through active transport the membrane controls the concentration of nutrients and ions within the cell by selecting which substances enter and leave and is therefore responsible for regulating the cell’s internal environment.

149
Q

It is generally accepted that the development of eukaryotic cells was one of the most important evolutionary advances.

Using examples, outline two ways in which internal membranes have been adapted to serve a range of useful functions in the cell. (2 marks)

A

The nuclear membrane separates the DNA from the rest of the cell.

*The endoplasmic reticulum provides a transport system.
*The cristae of the mitochondria provide a large surface area on which the reactions of respiration can occur.
*Compartmentalisation allows a large number of activities to proceed simultaneously.
Any two of the above or any two other appropriate examples were accepted.

biology level 3 (6 decks)

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